This invention relates generally to television receivers and particularly to fine tuning indicators for use with television receivers.
Television receivers generally provide a fine tuning control to permit a viewer to accurately tune the receiver to a selected television channel. However, most viewers are not able to determine precisely when the receiver is accurately tuned. Consequently, the television receiver may be inaccurately tuned and, as a result, not produce an optimum picture.
In the highly competitive television market, performance, reliability and cost are all of major concern. In this respect, adequate performing fine tuning indicators are generally cumbersome and expensive. Even though most "full feature" receivers include a form of automatic frequency control (AFC) for maintaining the tuner locked to the received signal, it is desirable to optimize receiver tuning prior to AFC activation. Consequently there is a need for fine tuning indicators to help the average viewer tune his receiver, at least initially before releasing the tuning system to AFC.
In video detection systems, the simple envelope detector has long been the most popular and have proven quite satisfactory. Recently however there has been a trend toward synchronous detectors, which offer enhanced performance.
The present invention offers attractive advantages with a receiver using a synchronous detector in that it uses the control voltage generated by the synchronous detector locking loop to control a fine tuning indicator, thus providing a reliable tuning indicator at a low cost.